<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		
		<form action="#" method="post">
			
		用户名：<input type="text" id="username"  name="username" value="梁博" /> <br/>
		密码：  <input type="password" id="password"  name="password" />
			
			<input type="submit" value="登录"/>
		</form>
		
		<script type="text/javascript">
			
			var  username = document.getElementsByName('username')[0];
			
			username.value = '冯坤龙';
			
			
		</script>
	</body>
</html>
